HOUSTON – Pete Harnisch said it was simply the biggest game of his life – and the ex-Met made the most of it, beating another old team, the Astros, 4-1 last night.

Harnisch, who has been battling shoulder woes and was making his first start in nine days, allowed only one run on four hits over eight innings. He did not walk a batter while striking out four. He threw only 79 pitches, 59 for strikes.

“This is a big win,” Harnisch said, “because it puts us up 2 games in the Wild Card and that’s what is really important. Winning the division would be nice, that would be a huge accomplishment, but it’s just a banner really. It’s not a big deal. I don’t look at the one game ahead; we’re 2 ahead. We don’t care how we get in the playoffs.”

Harnisch had his problems with Bobby Valentine, not going along with the program, so this win was big in other ways, too. “I never pitched in a big game with the Mets; we didn’t have any,” said Harnisch, who added he did not want to offer any thoughts on his days with Valentine, saying, “I’ll take the high road.” As for the slumping Mets, he noted, “They’ve lost seven games in a row. That was nice. They backed right past us.”

Reds manager Jack McKeon loves Harnisch’s attitude and leadership. “I knew he would come out and give us a great performance tonight,” McKeon said. “He is a gamer. He’s the kind of guy you want to have out there in a big game. He’s our ace in the hole. He’s super in the clubhouse, a great guy, all the crap I heard in New York I could not believe. This guy was rumored to be this or that, he’s the direct opposite. He’s one of my favorites. He may not be somebody else’s, but he’s one of mine.”

The ex-Fordham star from Commack, L.I., said the key for the Reds has been their ability to stick together as a team and the fact that the players have fun while playing the game, noting that McKeon has created the perfect atmosphere for the players to excel. It’s a team that loves to joke around with each other.

“There are a lot of guys with thick skin in this room,” Harnisch said. “You walk around here and you know you are going to get shredded pretty much, especially if you wear the wrong socks or you wear the wrong belt of if something is out of style or if you’re hair looks like that,” he cracked as reliever Danny Graves walked by with his spiked hair. “You can’t avoid it. So you had better be able to take it and you had better be able to give it out. We’ve got a lot of that around here, and that really helps keep a team loose.”

Even during the game, Harnisch was joking with teammates to keep it loose, telling them, “Don’t be afraid to get a couple of guys on base.”